Extech 6015WC Waterproof pH Electrode with Cable For Extech Model PH220-C Palm pH meter electrode with 4-wire waterproof connector and 39-Inch (1m) cable Rugged, polycarbonate construction 4-wire waterproof connector features glass pH sensing bulb surrounded by protective teeth Automatic temperature compensation via built-in Pt-100 Ohm sensor 0 to 14pH range